Thanks, it seems that actually something had got into a mess on our translation.
Moving the project directory to C:\temp forced a full download and all is now better.
The first few times it crashed there had been a message about unsaved data (with no opportunity to review it or do anything, as the content in the project window wasn't updating/moving/responding).
I don't know if some type of unsaved data would cause the crash, or how a version-upgrade would bring about that sort of unsaved data.